Grain harvesters have been in existence for many years. Originally developed to eliminate the arduous task of cutting grain by hand with a sickle or scythe prior to threshing, harvesters have evolved into large self-powered machines that are able to perform may steps that were once done by hand. With the modern self-propelled harvester, a single operator can now cut, thresh, and clean many acres of grain in a continuous operation—all from the comfort of an enclosed, air-conditioned cab. Modern grain harvesters typically include a large front facing header having a cutter bar and a horizontally rotatable reel with paddles or tines. The reel positions the crop relative to the cutter bar and sweeps or rakes it into the harvester after it has been cut from the stalk. The cut crop is then conveyed by a series of mechanisms, such as rotating augers and elevators, to a threshing station where the grain is separated from the crop, most often by a rotor that draws the crop past an arcuately shaped metal grill. The grain is then cleaned, usually by transporting it past a sieve or sifting mechanism, which is provided with a variable speed blower that introduces a stream of air therethrough in a generally vertical and angled direction, and which is powerful enough to carry comparatively less dense material, typified by chaff, away from the sieve, while allowing denser material such as grain to fall down through the sieve and into a collection bin for further processing. The chaff, along with other waste material such as the leaves and stems of the crop and the occasional tare, is then conveyed along the harvester by agitators, which shake out residual grains and unthreshed heads and send them back to be rethreshed, leaving the remainder of the waste material to be directed out of the harvester for subsequent disposal.
As will be appreciated, there may be occasions where not all of the grain will be recovered for re-threshing and some grain will be expelled along with the chaff. Thus, many harvesters are provided with one or more sensors that monitor grain as it passes thereby. These sensors often take the form of transducers that detect grain impacts, but they may also detect grain using acoustic or optical detectors, or microwaves, for example. The sensors are typically located adjacent to the chaff and tailing discharge chute of the harvester, and are connected to a meter that is located in close proximity to the operator of the harvester.
In operation, the aforementioned sensors will a produce a signal that is proportional to the amount of grain detected, and the signal will power the meter accordingly. Usually, the meter will be capable of indicating if there is no grain loss, if there is grain loss within an acceptable predetermined range of values, or if the grain loss is unacceptably high. As will be appreciated, the meter may be analog or digital. Operation is straightforward. If, for example, the amount of grain being discharged with the chaff and tare is below a predetermined threshold, the meter will not be actuated and the harvester may operate normally. If the meter indicates that the amount of grain being discharged with the chaff is within a predetermined range of values, the meter will be actuated and the operator will know that grain loss is elevated and that the operation of the harvester operation should be monitored more closely. If the meter moves past the upper range of normal operation, the operator stops the harvester so that it may purge itself. It will be appreciated that while the predetermined range of upper and lower values may be arbitrarily set, the upper value is usually chosen to represent the harvester's maximum capacity. Thus, it is desirable to make adjustments to the harvester before the upper value is exceeded. Usually the ground speed is reduced.
A drawback to the above system is that it is possible for the harvester to operate at or near the upper end of its meter's safe range of operation, which means that the harvester is operating at a comparatively high grain loss level. While such a condition may be acceptable for short periods of time, over the long haul grain loss may be substantial.
Another drawback is that in heavy and/or downed crop situations, the meter has to be monitored more carefully. This diverts attention to other aspects of the harvesting operation and it becomes easier for the operator to become distracted—with potentially serious consequences. Moreover, loss of grain that may be otherwise harvested leads to unprofitability.
There is a need for a control system that is able to minimize grain loss in a harvester. There is also a need for a control system that is able to simplify operation of a harvester by reducing the number of operational parameters that need to be monitored by the operator. There is also a need for a control system that is able to adjust an operating parameter of a grain harvester as the grain harvester is in operation. There is also a need for a control system that is able to adjust the operating parameter in response to a grain sensor signal. There is yet another need for a control system is able to adjust an operating parameter by forming at least one discrete circuit that is connected to, and which modifies the power supply of an operating parameter. There is still another need for a control system that is able to adjust the ground speed of a harvester. And there is a need for a control system that may be easily overridden by an operator of the harvester.